A short time after the Panchevo celebration, a number of scientists of the University of Belgrade, members of the Royal Serbian Academy, invited me to an informal conference, and asked me to tell them something about American science and its National Research Council in Washington. I do not think that on that occasion my discourse on this most interesting topic impressed my Serbian friends as strongly as my Panchevo discourse did. For a long time after this conference I thought of many things that I might have said, but did not say. The more I thought about it the more I was dissatisfied. I was informed several months after this conference that one of the Serbian scientists present remarked to a mutual friend that from my Panchevo address on American idealism he had been led to believe that at the Belgrade conference I would say something about idealism in American science. But I said nothing, and he inferred, therefore, that there could not be much idealism in American science, a thing which he had always suspected. Many European scientists suspected that long before he did. That permissible inference of the Serbian scientist hurt me, and it hurt the more because I felt that the omission was unpardonable. But the psychology at the Panchevo celebration was different from that at the conference in Belgrade. In Panchevo a remark was made from which, I was afraid, one might have inferred that this is a country of materialism. Nobody at the Belgrade conference suggested the thought that American science might, perhaps, have a taint of materialism. But, of course, no Serbian scientist could have suggested such a thing when the memory of the service of American science to Serbia during the typhus ravages of 1915 was still fresh in everybody’s mind. A fireplace fed by slow-burning wood must be stirred up often to maintain a lively flame. Similarly, the flame of a slow mental combustion cannot be maintained without occasional stirring. My mental combustion at the Belgrade conference was certainly slow, and needed a stirring up, similar to that which it received in Panchevo. My early studies of American history and American traditions would have proceeded much more slowly, if it had not been for my old friend Bilharz, who stirred me up with his prejudices against American democracy, and with his everlasting complaints against the imaginary spectre which he called American materialism.